A work-in-process (WIP) tracking system directs and monitors thenflow of product in a factory. The author describes a WIP tracking systemnthat supports the management of complex process plans, ensures thatnproducts receive their intended processing, and can be used to determinenthe actual processing received by finished products. The two majornfeatures of the tracker are the representation of process plans asnordered trees of parameterized subprocess plans, and the logging ofnprocess data at each process step. The tree representation encouragesnmodular process plans, which makes the plans easier to create andndocument, and is flexible enough to allow specific items to follownnonstandard subplans or to change plans after processing has begun. Thenlog makes it possible to reconstruct the entire processing sequence ofnan item and permits measurement values obtained earlier in an item'snprocessing to be used as the value of a later step's parameter, creatingna form of feed-forward process control
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